1. Field of the Invention
This invention is generally directed to lighting systems and more specifically to fiber optic lighting systems wherein a plurality of fresnel lenses are mounted within spaced openings provided in a front panel of a sign, signal or other light fixture housing and are spaced from the light emitting tips of one or more fiber optics that are mounted through a rear wall of the housing. The fiber optics are mounted through small openings provided in the rear wall of the housing and are positioned and aligned within the housing using a polycarbonate plastic shield. The one or more fiber optics may be generally aligned with and are within the focal distance of each of the opposing fresnel lenses so that either one or a plurality of light sources may be emitted through the fresnel lenses from the optical fibers. In the invention, the polycarbonate shield not only functions to align the fibers and prevent their further penetration relative to the spaced fresnel lenses but also reduces the amount of ultraviolet energy which is allowed to concentrate on the ends of the fiber optics from light entering through the fresnel lenses during periods of low ambient or natural sun angle. In some instances, it is possible that the plastic shield may be colored so as to filter the light being emitted to the lenses from the optical fibers. The plastic shield also works as a specular reflector for light which reflects off the interior surfaces of the fresnel lenses within the housing as each of the shields is formed having an arcuate or concave outer surface which opposes each of the lenses.
The lighting system of the present invention is particularly adaptable for use in commercial environments for signs and backlighting and especially highway signs which are exposed to sunlight wherein the ambient light directed towards the face of a sign will vary in incident angle depending on the time of day. By mounting the fresnel lenses recessed relative to the front of the signs or signals the lenses become self-shaded thereby reducing the requirement to provide separate shade elements which are incorporated with many conventional highway signals and signs while still allowing the light emitted from the signs, signals or housings, through the fresnel lenses, to be sufficiently intense to permit the use of the lighting systems even when low sun or other ambient light angles are encountered.
The fiber optic mountings utilized with the light systems of the present invention may further include structures which will enable the accurate retention of the fiber optics relative to the lenses associated with each lighting system.
2. History of the Related Art
The use of fiber optics in lighting systems is well known and has gained in commercial acceptance and usage over the past 10-15 years. An advantage of such systems is that light may be conducted from a remote source to a plurality of different areas utilizing individual light fibers which extend from the source to a point of light emission which may be at some distance from the light source. Utilizing such systems, a plurality of fiber optics may be associated with each light source.
Fiber optics have also been used for visual communication in traffic control. In western Europe, such fiber optic signs have been utilized to control pedestrian traffic and have been incorporated into signs which indicate to the pedestrian to either "walk" or "don't walk". In addition, such signs have been utilized for highway lane control by providing "X's" or "arrows" to direct or prohibit vehicular traffic in a given area.
Fiber optic signs were originally introduced based on the theory that they could provide brighter point source light illumination because of the inherent directional light output characteristics associated with fiber optic strands. Further, with the directional light emitting characteristics of fiber optics, it was theorized that the light images would be intense enough to permit distinction between closely spaced, discrete point sources of light. A further advantage believed of such systems was that the light sources could be easily replaced without having to replace the fiber optics themselves and thereby reduce maintenance in repair of signs, signals and other light systems incorporating fiber optics.
Unfortunately, to date, most such fiber optic signs have not provided directionalized light output which is sufficiently intense and clear so as to provide messages which are not mottled in appearance. Most conventional fiber optic highway type signs utilize glass fibers which are often inconsistent in the degree of light transmission from one fiber to another. Further, due to the small size of glass fibers, many fibers would have to incorporated in a single lens system. As glass fibers are inherently brittle, a great deal of expense is required to ensure the proper and safe mounting within a sign or optical system such as to protect against vibrations which could adversely affect the integrity of the fiber optics associated therewith.
As a result of the foregoing, in many conventional type fiber optic signs or lighting systems, the light intensity which is emitted from the system is not intense enough especially when ambient light conditions are such that a low angle of incoming light is directed upon the face of the lens system associated therewith. Under some conditions, such as when the fiber optics are used in highway or pedestrian control signs or signals, poor lighting intensity could be hazardous as pedestrians as well as motorists would not be able to easily discern messages being displayed.
Another problem inherent in conventional fiber optic sign or signal systems is that over a period of time the amount of ultraviolet light which impinges upon the fibers or the heat developed within the interior of such signs will adversely affect the fiber optics thereby further reducing the intensity of light which is emitted. Such a reduction in light intensity requires increased maintenance of such light systems which is undesirable and not cost effective. Also, in order to properly shade conventional fiber optic signs and light systems against low incident ambient sunlight, it is frequently necessary to provide separate awnings or shades which will reduce the amount of light which can enter into the lenses associated with such systems to ensure that sufficient illumination is maintained.